Heretofore, as magnetically working substances, such oxides and compounds containing oxygen as Dy.sub.2 Ti.sub.2 O.sub.7, DyPO.sub.4, Gd(OH).sub.3, and Gd.sub.2 (SO.sub.4).8H.sub.2 O have been treated as magnetic refrigeration materials and expected to find utility in cryogenic refrigeration near the liquefaction temperature of helium.
These compounds entail various restrictions and disadvantages: (1) They are deficient in magnetic refrigeration efficiency because their contents of magnetic elements (Dy, Gd, etc.) per molecular unit are small. (2) They are incapable of attaining desired refrigeration from a high temperature such as room temperature because their Curie point or Neel point is as low as about 10 T (K) at most. (3) Since these compounds possess the Curie point or the Neel point and, therefore, permit a simple refrigeration to be carried out rather efficiently only at and around such points, they cannot be expected to work effectively outside but narrow temperature ranges centering around such points. (4) Since they are compounds possessing low degrees of the thermal conductivity, they are deficient in refrigeration efficiency and its output. (5) Since they require a strong magnetic field ranging from several teslas to 10 teslas in generating their magnetical working, they are enabled to have magnetically working abilities by using only superconducting magnets which have come to be feasibilized recently.
This invention aims to eliminate the aforementioned restrictions and disadvantages related to the conventional magnetically working substances and provide novel and original magnetically working substances which, by virtue of adiabatic demagnetization, manifest magnetically working abilities with an extremely high efficiency in a wide temperature range under strong magnetic fields as well as under weak magnetic fields using superconducting magnets or even under weak magnetic fields using conventional electromagnets and, therefore, finds utility in applications to big plants for MHD power generation, nuclear fusion, and energy storage and to other various devices such as linear motors, electronic computers and their peripheral devices.